Analog to digital divider apparatus



July 13, 1965 A. B. WALLS ETAL ANALOG TO DIGITAL DIVIDER APPARATUS Filed May 3l, 1961 INVENTORS Allen B. Walls and James E. Thompson 'ATTORNEY U@ fw S E S S E N H W July 13, 1965 A. B. WALLS ETAL ANALOG TO DlGITAL DIVIDER APPARATUS 3 Sheets-Sheet 2 Filed May 5l, 1961 mv .mi

mOZmDGmw MEC. 2. wPDaHDO mmPZDOO -O-O-O-C-O-O-O mozmDGmw MEZ. zwFDnrPDO mPzDOO July 13, 1965 A. B. WALLS ETAL ANALOG TO DIGITAL DIVIDER APPARATUS 3 Sheets-Sheet 5 Filed May 31. 1961 United States Patent tiice aisles@ Patented July 13, 1965 lames E. Thompson, Se- .griors to Westinghouse Electric ttshurgh, lla., a corporation of The present invention relates to divital to analog converting apparatus, and more par arly to analog to digital divider apparatus for obtaining a digital number proportional to the quotient of two analog signals.

lt is often required to normalie two analog voltages obtain the quotient of these voltages in a digital numer orm. Generally, in prior art, this is accomplished by iirst converting both analog voltages into digital form, and then perfornlng the division digitally in a titer. Because of widely varying analog signal am- A nudes, it is required that a large numb-er of information bits be supplied in order to obtain the necessary precision over the total range. Also it is required to provide accurate reference voltage supply in the digital conversion or the analog voltase. Furthermore, since the analog signals must be cor x,rted into d .tal information, the converting time requirement is substantial. ln view of these problems:

is an object ol the present invention to provide a new and improvedv analog to digital divider.

lt is a further obiect of the present invention to provide a new and improved analog to digital divider which provides a digital number proportional to two analog signais without first converting the analog signals into digital form.

v4t is a further object ol the present invention to provide an analog to digital divider in which a digital number proportional to the quotient or two analog numbers is obtained while requiring only one converting operation.

The present invention broadly provides lan analog to digital converter wherein a digital quotient signal which is established in a quotient register is mutiplied by an analog divisor signal in a digital to analog multiplier to provide a signal which is the product of the quotient digital signal and the divisor analog signal. The product signal is compared with an analog dividend signal in a comparing circuit which in turn supplies an error signal that is applied to the quotient register to change the state ot he quotient register in a manner tending to correct the digi-,al quotient signal and so change the error signal; so that, the resulting digital signal after completion of the comparison routine is proportional to the quotient of the two analog signals.

These and other obiects will become more apparent in following detailed description and accompanying specilifation, considered in view of the drawings in which:

FIGURE l is a schematic-block diagram of one ernoodirnent of the present invention;

FGS. 2A and 2B are waveform diagrams to aid in the explanation of the operation of the embodiment of is a schematic-block diagram of another em bodnient of the present invention; and,

FlGS. 4A and 4B are waveform diagrams to aid in the explanation of the operation of the embodiment shown in riG. 3.

Referring to FIG. l, a counter lll is shown having outputs l, 2, 3, 4, 5 and d. Binary CNES or positive signals are provided at the terminals l through d in a time sequence. The AND gates l2, ld, lo, l5, and 22 receive the outputs from counter l as one of their inputs. A reset input Z/l is provided for the counter l A quotient register 25 comprises a plurality of binary flipllop circuits including sign flip-liep 2S, one-halt ilip-llop 3%, one-fourth llip-llop 32, one-eiohth iiip-lop 36, onesixtoenth iiip-ilop 3o, and one thirty-second flip-lop 38. The upper input terminals 44B, 452, 44, 46, 47 and 4S of the individual flip-dop circuits of the quotient register 26 are set inputs and the lower input terminals 5G, SZ, 54, 56 and are the reset input terminals. It is noted that the sign iiip-iiop 2&2 has only a set input which is taken from the output or" AND gate 12. The set inputs to terminals 42, 44, do, 47 and 4S are supplied from the outputs fl, 2, 3, fl, 5, respectively, of the counter il). A reset input 255 is provided for the quotient register 26. The reset inputs 24 and 25 may be used to restart the cycle oi operation. The other input for the AND gates l2, 14, lo, 3.55, 2@ and 22 is supplied from the feedback loop through lead et?. The outputs of the AND gates i4, lo, l, and 2.2 supply the reset input to the flip-flop circuits tl, 3?. 34, 3o and 33 respectively. The tlip-flop circuits 2.3, 3%, 3?., 34, 31; and 33 are so designed that a CNE at its set input will supply a SNE at its output. When a @NE is tien received at its reset input the output is then reset to a zero. The AND gates provide a ONE output when a ONE is r ceived at each of its inputs. The outputs o2, 6d, of, o8, 7u and 72 of the individual flip-liep circuits of the quotient register 26 are connected to the switches 74, 76, 78, Sti, S2 and 84 respectively. An analog divider voltage V is applied to amplifier which ampliies and inverts the polarity of the input analog voltage V. The output of the amplier 6 is applied through lead to the switches 7o, 78, Sil, 82 and Si respectively. Also the output of the amplilier $6 is applied through lead 9i) to the inverter 92 which inverts the polarity of the voltage applied thereto. The output of the inverter 92 is then applied to the switch '74. The switches are so designed that when a ONE is received at one terminal the switch then permits the analog signal applied to the other terminal to pass to the output. When a ZERO is received at one terminal, the output voltage is ero. These switches may be relays, controlled rectiiiers, or any other switch device well known in the art. rl`he output terminals of the switches 74, 76, 7S, 80, 82 and @d are respectively connected to the resistors R of the weighted resistive network 94. Between the resistors R are connected resistors R/Z having one-half the value of resistance or the resistors R. The output terminal of the weighted resistive network 94 is connected to one input of the summing amplifier 93. The other input of summing amplifier 95 is supplied with an analog dividend voltage E. The summing amplier dal takes the algebraic of the inputs and quantizes it to provide a binary ONE or ZERO output depending upon the magnitudes of its inputs. The output of the summing amplifier 9S is applied through feedback loop titl to the AND gates.

To aid in the explanation of the operation of the analog to digital divider of FlG. l reference should also be made to FIGS. 2A and 2B. It should be noted that the output of the weighted resistive network 94 is the product ot the divisor voltage "J and the digital number N in the quotient register 2d. As the function of weighted resistive networks in analog to digital multiplier' circuit is well known in the art it will not further be discussed herein. See Analog-Digital Conversion Techniques, Alfred K. Sussliind, The Technical Press of Massachusetts Institute of Technology and lohn Wiley and Sons., inc., 1957, chapter 5.

For purposes of explanation, assume that the quotient register starts in its reset position, ie., there is no number in the digital form. The counter lil provides ONE outputs in time sequence on its output terminals Il through 6. rthe CNE outputs are only of sufcient length to set the flip-flops of the quotient register 26, and there is suflicient timebetween outputs to avoid false resetting of the flipflops. Also assumethat the dividend voltage E is' +25 .1 volts and that the divisor voltage G is +32 volts. The steps of operation then are:

' (1) At the time sequence 1, the counter 10 provides a ONE at output terminal 1 as previously described. The ONE is received at the set terminal 42 of the one-half flip-flop 30 which is thereby set to apply a ONE to the switch 76. The switch 76 is thus actuated to allow the divisor voltage V to pass therethrough to the weighted resistive network 94, which attenuates this voltage to provide an output of -16 volts on lead 96. The summing amplifier 98 quantizes the signal applied thereto to provide a ZERO if the algebraic'sum ofits inputs is positive and a ONE if the algebraic sum of its inputs is negative. As the algebraic sum of the dividend voltage E and the product voltage N times Vis positive a ZERO is provided in this case, and the sign of the quotient N is determined as positive. If the dividend voltage E had been negative, the summing amplifier 98 would have provided a ONE to the AND gate 12, which would have caused the AND'gate 12 to provide a set signal to the sign flip-flop 28 as a ONEwould have also been applied from the counter at this time to the AND gate 12. The setting of the sign flip-flop 28 would have provided a signal to actuate the switch 74, which would have in turn allowed an inverted divisor voltage V to be passed thereto. The weighted resistive network would have ythen passed a voltage of 32-16 or a positive 16 volts to the summing amplifier 98; since the product output N times V of the weighted resistive network 94 and the dividend voltage E are of different polarities the summing amplifier 96 can converge, the divider circuit will then function an hereinafter explained. However, if the divisor voltage V were of a negative polarity it should be noted that the inputs of summing amplifier 9S would not converge and coverage, the divider circuit will then lfunction as herein the example both divisor and dividend voltages are assumed positive; thus the Asigny flip-flop would remain in its reset or positive condition.

(2) At time sequence 2 the counter 10 provides a ONE to the set input 44 of the one-fourth flip-flop 32 which in turn provides an actuating signal to switch 78 to allow the divisor voltage V to pass into the weighted resistive network 94. As the one-half flip-fiop 30 is in its set position the switch 76 also remains actuated and the divisor voltage V can pass therethrough. The output of the weighted resistive network on lead 98 is then'% times V or A '24 volts, as shown in FIG. 2B. The algebraic sum of the inputs of the summing amplifier 98 is still positive thus a ZERO is fed back to the AND gates overlead 60 so that none of the gates pass a signal to reset the flipflops of the register 26.

(3) At time sequence 3, a ONE is provided by the counter to the set terminal 46 of the one-eighth ipflop 34, which provides an activating signal to the switch 80 and thus allows the divisor voltage V to pass therethrough. The output on lead 96 of the weighted resistive network is then lof the divisor voltage V or @-28 volts. As this product voltage exceeds -negatively the dividend voltage E the summing'amplifier 98 now provides a ONE in the feedback loop 60.

(4) At time sequence 4, a ONE is provided by the counter 10 to the set terminal 46 of the one-sixteenth flipflop 36 which provides an output signal to activate switch 82." Also, however, the counter 10 provides through outp'ut terminal 4 an input to the AND gate 18 which also has a ONE input from the feedback loop 60, thus the onee'ighth flip-flop 34 is reset, and no longer provides a ONE output, as is shown in FIG. 2A. The one-half and onefour'th flip-flops remain set, however, as there are now no outputs from counter terminals 2 and 3. The switches 76, 748 and 8 2 are thus responsive to pass the divisor voltage V to the weighted resistive network 94, Vwhose output now is 1%6 times the divisor voltage V or -26 volts. Because the algebraic sum of the inputs of the summing amplifier 98 is still negative, the summing amplifier again provides a ONE to the feedback loop 60.

(5) At the time sequence 5, a ONE is provided by the counter 10 to the set input 48 of the one-thirty-second flip-*iop 38-which provides a ONE output to activate switch d4. A ONE being on the feedback loop 60 causes the AND gate 20 to provide a reset signal to the onesixteenth dip-lop 36. The switches 76, '78 and 84 are now responsive to allow the divisor voltage V to pass therethrough to the weighted resistance network 94. The output of the weighted resistive network on lead 96 is then 25/32 of the divisor voltage V or a '-25 volts; this causes summing amplier 98 to provide a ZERO to the feedback loop 60 as the algebraic sum of the product signal N times V and the dividend voltage E is positive. The digital number now set in the quotient register is 2%2.

(6) At time sequance 6, a ONE is provided by the counter 10 to one input of the AND gate 26, however, as azeno is on the feedback loop 60 the AND gate is non-responsive to provide an output to reset the onethirty-second flip-flop 38. Within the accuracy of the quotient register then the quotient in digital form of the vdividend voltage E in the divisor voltage V is 25/32. The resultant settings in the quotient register 26 are shown in FIGURE 2A.

FIG. 3 provides an analog to digital divider capable of handling negative analog divisor voltages as well as negative dividend voltages. Reference should also be made to FIGS. 4A and 4B to aid in the understanding of the Ioperation of the analog to digital divider of FIG. 3. Assume for purposes of example that the quotient register 26 starts in its reset condition and that the dividend voltage E is 25.1 volts and that the divisor voltage V is -32 volts. The steps of operation then are:

(1) The first cycle of operation is to determine whether the divisor voltage V is negative. At the time sequence 1, the counter provides a ONE at output terminal 1 which passesthrough lead 99 to input terminal A of the negative divisor flip-dop 102. The negative divisor flip'- op 102 is designed so as to have a reset output at terminal C of ZERO and a ONE at terminal D. If, however, ONES appear at input terminals B and A the flip-flopv is set so that the output at terminal C is a ONE and at terminal D is a zero. The negative divisor voltage V being applied to the amplifier 186 is inverted in the amplifier and applied to the sense amplifier 100. The sense amplifier 100, which may be an emitter or cathode follower does not invert the polarity of its input signal but provides an output signal of the same polarity; thus with a negative divisor voltage V a positive signal is applied from the sense amplifier 100 to input terminal B of the negative divisor flip-flop 102. This causes the flip-flop 102 to reset so that a ONE is applied to AND gate 104 and a zero is applied to AND gate 106.

(2) At time sequence 2, a ONE is applied to the set input 142 ofthe one-half flip-flop 130 of the quotient register 126. The one-half flip-flop then provides an actuating signal to the switch 176 to permit the input divisor voltage V to pass therethrough. The output of the weighted resistive network 194 is then one-half times the divisor voltage V or 16 volts as shown in FIG. 4B. The algebraic sum of the inputs to the summing amplifier 198 is negative so it provides a ONE to the inverter 108 and to one input of the AND gate 106.

l As the other input to the AND gate 106 is supplied with a ZERO from the output terminal D of the negative divisor flip-flop 102, it does not provide an output signal to the OR gate 200. The ONE output of the summing amplifier is inverted .in the inverter 108 thus appears as a zero input to the AND gate 104. Thus the AND gate 104 does not provide an output signal to the OR gate area-,95o

c.) and so a ZERO is applied to the feedback loop ldd. The one-half flip-dop l@ then remains in its set position. it should be noted that if either one but not both or" the divisor voltage V and the dividend voltage E had been negative, the feedback path lo@ would have supplied a ONE to the AND gate 1l?. to so set the sign flip-flop 12S to its negative set position.

(3) At time sequence 3, a ONE is applied to the onefourth llip-ilop 132 to set it and so activate switch T178. The output of the weighted resistive network is then 24. volts, but the algebraic sum of summing ampliiier still being negative a ZERO is still applied to the feedback path lo@ and the one-half and one-fourth hip-flops remain set. I

(4) At the time interval 4, a ONE is provided to the one-eighth dip-dop E34 to set it and supply an activating signal to the switch lid-ll. The weighted resistive network then provides a product signal of N times if or 2S volts to the summing amplier 193. rEhe algebraic sum of the summing ampliers inputs now being positive, a Zero is applied to the inverter lti which in turn supplies a ONE to the AND gate 34. However, as the negative divisor dip-flop @2 is `in its set position, a ONE is also applied to the AND gate lil-4;- from the C terminal of the negative divisor flip-flop MZ; therefore the AND gate trt supplies a ONE to the OR gate This in turn applies a ONE to the feedback path See FIG. 4A.

(5) At time sequence 5, a ONE is applied to one input of the AND gate lit which also has a ONE applied to its other termiI l from the feedback path i169. Thus, the AND gate 1 applies a ONE signal to reset the oneeighth dip-flop 134. A ONE is applied also at this time to the one-sixteenth flip-flop 136 to set it and so activate the switch 32. The output from the Weighted resistive network is then 26 volts, as shown in EEG. The algebraic sum of the inputs of the summing amplifier 198 remaining positive again applies a ONE to the feedback loop Mill.

(6) At time sequence 6, a ONE is provided to an input of the AND gate 120 from the counter liti and also to another input from the feedback path ttl, and so the AND gate l2@ is responsive to reset the onesixteenth ip-ilop Also at this time the one-thirtysecond hip-flop is set and the gate i8@ is responsive to pass the divisor voltage V to the weighted resistive network H4. The product signal then to the summing amplifier 193 is 25 volts. The negative algebraic sum of the inputs of the summing amplier 193 causes the summing amplifier 98 to have a ONE output and so a ZERO appears on the feedback path 16th.

(7) At time sequence 7, a ONE is applied to the AND gate 122. However, as a ZERO appears in the feedback path 160 the AND gate 122 is non-responsive to reset the one-thirty-second flip-flop 138. rThe digital number now in the quotient register 12d is 2%2, which is the quotient within the accuracy of the quotient register of the dividend voltage E and the divisor voltage V. The digital settings in the quotient register 126 are shown in FIG. 4A.

The accuracy of the analog to digital dividers of FIGS. l and 3 can, of course, be increased by increasing the capacity of the quotient registers, the counters and adding additional switches and additional legs to the weighted resistive networks.

Although the present invention has been described with a certain degree of particularity, it should be understood that the present disclosure has been made only by way of example and that numerous changes in the details of the circuitry and the combination and arrangement of elements may be resorted to without departing from the scope and the spirit of the present invention.

We claim as our invention:

1. In analog to digital divi-der apparatus for producing digital signals representing the quotient of analog divi- LUZ dend signals and analog divisor signals, said apparatus being capable of handling either one of negative divisor and negative dividend signals, the combination of: quotient means operative to supply quotient signals in digital form; multiplying means operatively connected to receive said divisor signals in analog form and said quotient signals, and being `operative to provide product signals of said quotient and divisor signals; feedback comparing means operatively connected to receive said dividend signals in analog form and said product signals, and being operative to supply error signals to correct said quotient signals to be indicative of the algebraic sign and magnitude of the quotient yof said dividend and divisor signals; and sensing means operatively connected to said comparing means and being responsive to cause said dividend and product signals applied to said comparing means to be of opposite polarities.

2. A divider for producing a digital signal representing the quotient of an analog dividend signal and an analog divisor signal, said divider comprising a quotient register having a plurality of stages, one of said stages being an algebraic sign stage, means for operating said register stages in turn, means for multiplying the analog divisor signal with an analog signal the magnitude of which becomes progressively larger in decreasing incremental steps as said stages are operated in turn to produce a product signal, means for comparing the magnitude of said product signal with the magnitude of the dividend signal and for producing a feedback signal only when the magnitude of said product signal exceeds the magnitude of said dividend signal, and means controlled by said feedback signal for resetting the last stage operated in said quotient register whereby the nal setting of said quotient register represents the digital value of the algebraic sign and magnitude of the quotient of said dividend and divisor analog signals.

3. In analog to digital divider apparatus for producing digital signals representing the quotient of analog dividend signals and analog divisor signals being capable of handling either one `of negative dividend and negative divisor signals the combination of: quotient means operative to provide quotient signals in a digital number form; sequencing means operatively connected to said quotient means and being operative to control said quotient means; multiplying means operative to receive said divisor signals in analog form and said quotient signals, said multiplying means including a plurality of switching means operatively connected to said quotient means and operative to pass said divisor signals in response to said quotient signals, and a weighted resistive network operatively connected to said switching means and being operative to provide product signals oi said divisor signals and said quotient signals; feedback comparing means operative to receive said dividend signals in analog form and being operatively connected to said resistive network to receive said product signals, said feedback comparing means being operative to supply error signals to said sequencing means in a relation to correct said quotient signals in digital number form to be indicative of the algebraic sign and magnitude of the quotient of said divisor and dividend signals in analog form; and sensing means operatively connected to said comparing means and being responsive to said signals applied to said cornparing means to have opposite polarities.

References Cited by the Examiner Instruments & Automation: vol. 30, 10/57, pages 1877- 1880.

Palesky, Hybrid Analog-Digital Computing Systems.

IBM Technical Disclosure Bulletin: vol. 2, No. 4, 12/59, pages 133 and 134.

MALCOM A. MORRISON, Primary Examiner.

WALTER W. BURNS, IR., Examiner. 

1. IN ANALOG TO DIGITAL DIVIDER APPARATUS FOR PRODUCING DIGITAL SIGNALS REPRESENTING THE QUOTIENT OF ANALOG DIVIDEND SIGNALS AND ANALOG DIVISOR SIGNALS, SAID APPARATUS BEING CAPABLE OF HANDLING EITHER ONE OF NEGATIVE DIVISOR AND NEGATIVE DIVIDEND SIGNALS, THE COMBINATION OF: QUOTIENT MEANS OPERATIVE TO SUPPLY QUOTIENT SIGNALS IN DIGITAL FORM; MULTIPLYING MEANS OPERATIVELY CONNECTED TO RECEIVE SAID DIVISOR SIGNALS IN ANALOG FORM AND SAID QUOTIENT SIGNALS, AND BEING OPERATIVE TO PROVIDE PRODUCT SIGNALS OF SAID QUOTIENT AND DIVISOR SIGNALS; FEEDBACK COMPARING MEANS OPERATIVELY CONNECTED TO RECEIVE SAID DIVIDEND SIGNALS IN ANALOG FORM AND SAID PRODUCT SIGNALS, AND BEING OPERATIVE TO SUPPLY ERROR SIGNALS TO CORRECT SAID QUOTIENT SIGNALS TO BE INDICATIVE OF THE ALGEBRAIC SIGN AND MAGNITUDE OF THE QUOTIENT OF SAID DIVIDEND AND DIVISOR SIGNALS; AND SENSING MEANS OPERATIVELY CONNECTED 